moving house panel to new location

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robh

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Oregon..Not Orygone
This may be a silly question but I'm an industrial guy. If you were to use the original box as a splice point, what is the best method for splicing everything together? Wire nuts? Terminal blocks?
 
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Barndog

Senior Member
Location
Spring Creek Pa
infinity said:
Let's assume 8-20 amp (#12 AWG) circuits in one raceway. By using MWBC's you would have 8 CCC's which would require a derating of 70%.

30 amps * 70% = 21 amps so you're still good.

Now use the same 8 circuits with separate neutrals which equals 16 CCC's and would require a derating of 50%.

30 amps * 50% = 15 amps so your 20 amp circuits with #12 conductors are no good.

When using separate neutrals you could only get 4 circuits in the raceway (only 1/2 of the number you would with a MWBC setup) and still maintain the 20 amp rating for the #12 conductors. Not to mention the MWBC would save you on conduit fill as well.
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i have a question on this. if use share neutrals. whouldnt you have 12 CCC's because your neutrals would be CCC's unless you have balenced load on each phase. because if you use single neutrals you say you have 16 CCC's. just wondering what the differance between the two senerios are????

thanks
 
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infinity

infinity

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The neutrals would not be considered CCC's in a MWBC since they only carry the unbalanced current. Therefore with 8 circuits from 3-wire MWBC's you would only have 8 CCC's which leads you to a 70% derating. Take a look at 310.15(B)(4)(a).
 
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shaw0486

Senior Member
Location
baltimore
infinity said:
Splicing in the attic isn't a problem but you might need to make an ambient temperature adjustment for the conductors in the raceways. I would use a pull box to avoid the potential for derating in the wireway if you exceed 30 CCC's at any cross section. MWBC's are fine and will help you cut down on the number of CCC's in each raceway by up to 1/2.
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How will this cut down on ccc
 
infinity

infinity

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shaw0486 said:
How will this cut down on ccc
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Here's the calculation from post #8.

Let's assume 8-20 amp (#12 AWG) circuits in one raceway. By using MWBC's you would have 8 CCC's which would require a derating of 70%.

30 amps * 70% = 21 amps so you're still good.

Now use the same 8 circuits with separate neutrals which equals 16 CCC's and would require a derating of 50%.

30 amps * 50% = 15 amps so your 20 amp circuits with #12 conductors are no good.

When using separate neutrals you could only get 4 circuits in the raceway (only 1/2 of the number you would with a MWBC setup) and still maintain the 20 amp rating for the #12 conductors. Not to mention the MWBC would save you on conduit fill as well.
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Basically in this example each MWBC, two ungrounded conductors (circuits) and a shared neutral, would only be counted as 2 current carrying conductors since the neutral would only carry the unbalanced current. [310.15(B)(4)(a)] Having said that it does not count as a CCC for derating purposes. This is important since separate neutrals would double the amount of CCC's in the raceway and could significantly alter the derated ampacity of the conductors as in the example above.
 
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shaw0486

Senior Member
Location
baltimore
infinity said:
Here's the calculation from post #8.



Basically in this example each MWBC, two ungrounded conductors (circuits) and a shared neutral, would only be counted as 2 current carrying conductors since the neutral would only carry the unbalanced current. [310.15(B)(4)(a)] Having said that it does not count as a CCC for derating purposes. This is important since separate neutrals would double the amount of CCC's in the raceway and could significantly alter the derated ampacity of the conductors as in the example above.
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I think you are miss interpretting this code. The only way that a neutral would not be considered a non current carrying conductor is if it is carrying the unbalanced load of the same circuit such as a dryer, VAV, etc..

Therefore i dont feel that a neutral conductor of a multi wire branch circuit can be considered a non - current carrying conductor.
 
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jwjrw

jwjrw

Senior Member
shaw0486 said:
really where does it say that plain as day.
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I believe if you look in the article sited and read 310.15(b)(4) a, b .and c you will see when it is and is not counted as a ccc.

EDIT: I didn't read the first part of the thread but I saw the article posted and remembered the article stated when it the neutral is and is not a ccc.. Maybe it does apply maybe it doesn't.
 
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shaw0486

Senior Member
Location
baltimore
I dont feel that article states anything about a multi wire branch circuit specially plain as day.

Can alyone else put any insight into what this article is stating.

Thanks,
 
roger

roger

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Location
Fl
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shaw0486 said:
I think you are miss interpretting this code. The only way that a neutral would not be considered a non current carrying conductor is if it is carrying the unbalanced load of the same circuit such as a dryer, VAV, etc..

Therefore i dont feel that a neutral conductor of a multi wire branch circuit can be considered a non - current carrying conductor.
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Only if the major portions of the loads are non linear, otherwise it is not a CCC.

Roger
 
jwjrw

jwjrw

Senior Member
shaw0486 said:
I dont feel that article states anything about a multi wire branch circuit specially plain as day.

Can alyone else put any insight into what this article is stating.

Thanks,
Click to expand...


310.15(b)(4)(a) states when the neutral carries the unbalanced load of a circuit. If it shares a neutral it is a MWC.
 
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